Torsion Analysis for Cold-Formed Steel Members Using Flexural Analogies

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The design of cold-formed steel members must consider the impact of torsional loads due to transverse load eccentricity. Open cross-sections are particularly susceptible to significant twisting and high warping stresses. Design requirements for combined bending and torsion were introduced in the American Iron and Steel Institute Specification in 2007, and more recently in the Australian/New Zealand Standard 4600:2018. These provisions require an understanding of the distribution of internal forces and stresses due to torsional warping, which is not commonly taught in engineering curriculums. Furthermore, most structural analysis programs do not properly consider torsional warping stiffness and response. The purpose of this paper is to educate the structural engineer on torsion analysis using analogies to familiar flexural relationships. Useful formulas are provided for determining torsional properties and stresses.